AUTHOR=Lou Xueyuan , Li Xin , Li Aixia , Pu Mingyu , Shoaib Muhammad , Liu Dongcheng , Sun Jiazhu , Zhang Aimin , Yang Wenlong 

TITLE=The 160 bp Insertion in the Promoter of Rht-B1i Plays a Vital Role in Increasing Wheat Height

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00307

DOI=10.3389/fpls.2016.00307

ISSN=1664-462X

ABSTRACT=<p>The extensive use of two alleles (<italic>Rht-B1b</italic> and <italic>Rht-D1b</italic>) at the <italic>Rht-1</italic> locus in wheat allowed dramatic increases in yields, triggering the so-called “Green Revolution.” Here, we found that a new natural allelic variation (<italic>Rht-B1i</italic>) containing a single missense SNP (A614G) in the coding region significantly increased plant height against the genetic background of both <italic>Rht-D1a</italic> (11.68%) and <italic>Rht-D1b</italic> (7.89%). To elucidate the molecular mechanism of <italic>Rht-B1i</italic>, we investigated the promoter region. Sequence analysis showed that the <italic>Rht-B1i</italic> promoter could be divided into two classes depending on the presence or absence of a specific 160 bp insertion: <italic>Rht-B1i-1</italic> (with the 160 bp insertion) and <italic>Rht-B1i-2</italic> (without the 160 bp insertion). The promoter of <italic>Rht-B1i-1</italic> contained 32 more possible <italic>cis</italic>-acting elements than <italic>Rht-B1a</italic>, including a unique auxin response element AUXREPSIAA4. Quantitative RT-PCR analysis indicated that the 160 bp insertion is likely to promote the transcription of the <italic>Rht-B1i-1</italic> gene. The coleoptile lengths of wheat varieties treated with IAA, GA<sub>3</sub>, and IAA/GA<sub>3</sub>, combined with the histochemical staining of transgenic <italic>Arabidopsis</italic> containing the <italic>Rht-B1i-1</italic> promoter, showed that the height-increasing effect of <italic>Rht-B1i-1</italic> may be due to the synergistic action of IAA and GA<sub>3</sub>. These results augment our understanding of the regulatory mechanisms of <italic>Rht-1</italic> in wheat and provide new genetic resources for wheat improvement.</p>